In the “W-CDMA system” which has been studied in the 3GPP, a system has been studied recently which is capable of providing voice communication and non-voice communication by connecting a conventional mobile communication network to a network utilizing the Internet Protocol (IP network).
Such a system is referred to as an IMS (IP Multimedia Subsystem).
The IMS has been considered so that not only non-voice communication (for example, data communication and the like) but also voice communication having high requirements for delay can be provided through the IP network. In the Non-Patent Document 1, a channel for voice communication used in the IMS is defined.
However, when allocating a normal dedicated channel (DCH) to a channel for voice communication in the IMS, it is necessary to secure a bandwidth by assuming a highly bursty traffic, such as an RTCP signal (Real time Transport Control Protocol) or an SIP signal (Session Initiation Protocol). This results in problems of inefficiency in the use of radio resources (hardware resources) and of reduction in the network capacity.
In addition, the channel for voice communication guarantees a bandwidth not only for a usually-transmitted RTP signal (voice data) on which a header compression is performed, but also for other signals (for example, an RTP (Real time Transportation Protocol) signal on which a header compression is not performed, an SIP signal, an RTCP signal or the like), so that there is also a problem of inefficiency in the use of a radio resource (hardware resource).
[Non-Patent Document 1] 3GPP TS34.108 6. 10. 2. 4. 1. 5a. 1. 1. 1